1. Field of the Invention
The present invention relates to a wire electric discharge machine controller, wire electric discharge machine, and wire electric discharge machining method that permit change of the amount of compensation for wire radius compensation to be applied to a machining route programmed in a machining program.
2. Description of the Related Art
In machining of a workpiece with a wire electric discharge machine, if machining is conducted with the traveling route of a wire electrode being set as programmed in a machining program, the resulting size of the workpiece becomes smaller by the radius of the wire electrode plus discharge gap. To address this, a machining route on which the wire electrode moves is typically created by applying a certain amount of wire radius compensation (wire electrode radius plus discharge gap) to the route of the machining program. The amount of such wire radius compensation is determined through preliminary machining experiments in consideration of conditions including wire electrode type and/or machining speed.
Japanese Patent Application Laid-Open No. 4-2414 discloses an offset setting device for a wire-cut electric discharge machine that is capable of modifying the finished size of a workpiece by making modification to the amount of wire radius compensation. This device is intended to cut a workpiece into an intended shape by generating electric discharge between the wire electrode and the workpiece, and preprograms a reference offset for the wire electrode for a workpiece of interest, modifies the reference offset with an amount of modification, and sets the modified value as the amount of offset.
When the finished size of the workpiece differs from the intended size as a result of machining using the calculated amount of wire radius compensation, a machining result with the intended size can be yielded by modifying the amount of wire radius compensation by the difference between the machining result (i.e., the finished size of the workpiece) and the intended size. Another possible way to obtain a machining result of the intended size is to include a finishing allowance (i.e., an amount by which wire radius compensation is modified) in the workpiece size and modify the amount of wire radius compensation by the finishing allowance.
The offset setting device for a wire electric discharge machine disclosed by Japanese Patent Application Laid-Open No. 4-2414 only uses an amount of offset modification for one purpose. In a case where different amounts of offset modification should be separately used for different purposes, such as adjusting the amount of discharge gap in relation to the difference between the nominal material of a workpiece and/or a wire electrode and its/their actual material, adjusting the amount of machining in consideration of coefficient of expansion associated with workpiece temperature, and specifying the amount of finishing machining, the amounts of modification for such individual purposes need to be summed up. However, summation of the amounts of compensation for different purposes makes the original individual amounts of modification indistinguishable, resulting in the difficulty of modifying only one of the amounts of modification.
In a case where an amount by which the amount of wire radius compensation is modified due to a finishing allowance is set, the finishing allowance (i.e., the amount by which the amount of wire radius compensation is modified) can be specified at the beginning of a machining program or at a number of points in the machining program in order to set different finishing allowances for different portions being machined.
If the workpiece is not finished in the intended size as a result of machining with finishing allowances thus specified in the machining program, the finishing allowances need to be further changed by the difference between the machining result (i.e., the workpiece size) and the intended size.
Change to the finishing allowances is however burdensome as it involves alteration to the machining program and also poses a possible risk of omitting to make a modification when the program should be modified in many places. Also, when the sum of individual amounts of modification for different purposes is set as the amount by which the amount of wire radius compensation is modified, it is difficult to modify only the amount of modification for a particular purpose because the original individual amounts of modification before being summed up become indistinguishable.